Electric discharge device and method of making same



Aug. 26, 1958 E. B. FEHR ETAL ELECTRIC DISCHARGE DEVICE AND METHOD OFMAKING SAME Filed May 12, 1953 Inventors: Edith B. Pei-n 5 ase,

Allen P. Ha

Th eir Atb orn e5.

2,849,639 Patented Aug. 26, 1958 ELECTRIC DISCHARGE DEVICE AND METHOD OFMAKING SAME Edith B. Fehr, Schenectady, N. Y., and Allen P. Haase,

Owensboro, Ky., assignors to General Electric Company, a corporation ofNew York Application May 12, 1953, Serial No. 354,502

3 Claims. (Cl. 313-261) The present invention relates to improvedelectric discharge devices and a method of making same and moreparticularly to an improved electrode mounting.

It has been common practice in the mass production of electric dischargedevices, particularly of the receiving type, to support the variouselectrodes in mutually insulated and properly spaced relation by meansof insulating disks of mica engaged by the ends of side rods or otherprojections extending from the electrodes. The present inventioninvolves the concept of supporting the electrodes in spaced andinsulated relation by means of a flexible tape which is Wound upon theelectrodes at the opposite ends thereof, and it is an important objectof the present invention to provide an electric discharge deviceembodying this concept which offers substantial advantages overconventional structures particularly from the standpoint of automaticmounting of the electrodes. The invention also makes possible a moretruly concentric design by eliminating the necessity for additionalelectrode supports such as the grid side rods which tend to distort thefield between the electrodes.

Further objects and advantages of our invention will become apparent asthe following description proceeds, reference being had to the drawingand its scope will be pointed out in the appended claims. In thedrawing, Fig. 1 is an elevational view, partially broken away, of anelectric discharge device embodying our invention; Fig. 2 is aperspective view showing a portion of the electrode mount of the deviceof Fig. 1, and Fig. 3 is a perspective view illustrating a preferredmethod of mounting electrodes of the device shown in Fig. 1.

Referring now to the drawing as shown in our invention embodied in anelectric discharge device, which for purpose of simplification has beenillustrated as the triode type and includes a cathode sleeve 1, a gridmember of mesh type 2, and a cylindrical anode 3 mounted in concentricrelation in the order named. In accordance with the present invention,these electrodes are supported in mutually insulated relation by bodiesof insulating material 4 and 5 located between the cathode and grid andgrid and anode respectively and at both ends thereof. These layers orbodies of insulating material are in accordance with the presentinvention built up by wrapping on the electrodes in succession aplurality of layers of flexible tape having suitable properties for usein electric discharge devices. As well understood by those skilled inthe art, these properties include good electrical properties and inaddition freedom from elements which will be liberated during processingof the tube with detrimental effects on the discharge device,particularly on the cathode, and which does not tend to evolve anyappreciable amount of gas after the original processing of the tubeduring its manufacture. The insulating material may, for example, beflexible sheet asbestos preferably containing a small amount ofbentonite or a flexible mica sheet material prepared from mica flakes.The asbestos sheet material may be, for example, of the type disclosedin Walters Patent 2,493,604, dated November 6, 1944, and assigned to theassignee of this invention, and the mica sheet matereial may, forexample, be prepared in the manner described in de Senarclens Patent2,614,055, dated October 14, 1952.

As illustrated in Fig. 1, the mount may be supported Within an enclosingenvelope 6 by relatively rigid conductors 7, 8 and 9 connectedrespectively between the grid,cathode and anode and certain of thelead-in conductors 10. The ends of the heater element 11 are alsoconnected to separate lead-in conductors.

The features and advantages of our invention will be better understoodby a consideration of the method of assembly of the device illustratedin Fig. 1. A partially completed mount assembly is shown in perspectivein Fig. 2 and the method of effecting that assembly is illustrated inFig. 3. As shown in Fig. 3, the cathode cylinder 1 is supported from asuitable mandrel 12 for rotation about the axis of .the cathode. Stripsof flexible insulating tape of the type previously described are appliedin a succession of layers near the opposite ends of the cathode sleeve.They are preferably applied by rotating the mandrel 12 to wrap the tape.In starting, the tapes may be retained on the cathode sleeve in anysuitable manner, as by sticking with an adhesive or, if desired, bythreading into a slot formed in the cathode sleeve. As illustrated inFig. 3, the grid is in the form of a rectangular sheet of mesh material.While this grid material may be formed in a number of Ways, a processknown as electroforming is particularly adapted for manufacture of gridssuitable for use in accordance with the present invention. In accordancewith that process, the grid design is photographically reproduced on aresist coated surface and the resist developed, and the grid produced byelectroplating on the developed surface. As illustrated, the rectangularsheet 15 of the grid material is fed onto the strips of tape 13 and 14at the desired time which, of course, determines the number of layers oftape that have been applied to the cathode and in this way determinesthe cathode-grid spacing. The dimension of the grid sheet 15 may be justslightly less than the circumference of the bodies of insulatingmaterial 4 that have been built up respectively by the successiveapplications of the strips of tape 13 and 14, so that the edges of thegrid fail to meet by an amount sufiicient to allow the passage of thetape therebetween. In this manner the Winding of the tape may becontinued without any interference from the adjacent edges of the gridmember. As an alternative, the grid sheet could be notched slightly atthe regions of tape as shown at 16. If desired, the grid material may beslightly longer than the circumference of the tape so that there is aslight overlap at the ends of the grid sheet. While this tends toincrease the amount that the grid departs from a true cylinder, itinsures that there are no areas through which electrons can travel tothe anode without being controlled by the grid mesh. The winding of thetape is then continued until a suflicient number of layers have beenapplied to give desired grid-anode spacing and then the anode, which islikewise formed as a rectangular blank, is applied and the overlappingedges spot-welded to retain the mount in assembled relation. If desired,the anode may be formed with a standing seam with the edges thereofoverlapping and extending outwardly as illustrated at 17 in Fig. 1. Thebodies of flexible tape added after the grid are illustrated in Figs. 1and 2 at 5.

As an example of an electric discharge device embodying our invention,the cathode sleeve having an outer diameter of .045 inch Was assembledwith a grid member approximately l4 inch in circumference and a platemember essentially inch in circumference. The tape employed was of theclay containing asbestos type and included two strips approximately 4inches long and .030 inch wide. The tape was wound with five layersbetween the grid and cathode and ten layers between the grid and anode,the tape being .002 inch thick and giving a grid to cathode space ofapproximately .0l'inch and a grid to anode space of approximately .020inch. In the device just described'the grid material'was also .002 inchthick, the same as that of'the insulating tape. This relationshipbetween the thickness of the grid material and the insulating tape isnot essential. It is apparent that the thinner the insulating tape, theless the grid cross section departs from a true circle.

In the specification, the various electrodes have been described ascylindrical, even' though it is apparent that the inner electrode of theassembly may have an oval or even a rectangular cross section. When theinner electrode is non-circular, it may be oriented with respect to thestarting point of the tapes to either render the next electrode more orless circular than the inner electrode. In the appended claims theelectrodes are therefore referred to as tubular and as-being mounted insubstantial coaxial relation.

It is clear from the foregoing description that the present inventioninvolves an improved electrode mount assembly for electric dischargedevices including a novel method of assembling such mounts which issimple and particularly suited for mass production of electric dischargedevices such as those commonly used in radio receivers. While a simpletriode device has been selected for purposes of illustration, it will beapparent to those skilled in the art that any number of electrodes maybe employed in accordance with the present invention. It will also beapparent that one of the wrappings of the insulating material may beomitted if the insulating material has suflicient width with respect tothe length of the electrodes to provide the desired support.

While we have shown and described a particular embodiment of ourinvention, it will be apparent to those skilled in the art that changesand modifications may be made without departing from our invention inits broader aspects and we intend, therefore, in the appended claims tocover all such changes and modifications as fall within the true spiritand scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. An electrode assembly for an electric discharge device comprising apair of coaxial rolls of continuous insulating tape each havingsuccessive turns superimposed, a first electrode having oppositemarginal edge portions interleaved between a pair of successive turns ofthe respective rolls and having its major portion extending between saidrolls, and a second electrode having opposite marginal edge portionswrapped around and supported by the respective rolls with its majorportion extending between the rolls in spaced relation to said firstelectrode, the major portions of said electrodes being separated only byfree space forming an unobstructed electron flow path between saidelectrodes.

2. An electrode assembly for an electric discharge device comprising asupport, a roll of continuous insulating tape wound on the support withsuccessive turns of the roll superimposed, a first electrode having onlya marginal edge portion interleaved between a first pair of successiveturns of the roll and having its major portion extending beyond the sideedges of said turns, and a second electrode having only a marginal edgeportion wrapped around a. later turn of the roll and having a majorportion extending beyond the edge of the roll in spaced confrontingrelation with said first electrode, the confronting portions of saidelectrodes being separated only by free space forming an unobstructedpath for flow of electrons between said electrodes.

3. In an electron discharge device, a tubular first electrode, aplurality of spaced rolls of continuous flexible insulating tape Woundon the first electrode with successive turns of each rollsuperimposed, aconcentric second electrode extending between the rolls and interleavedbetween a first pair of successive turns of each roll, and a concentricthird electrode extending between the rolls wrapped around a later turnof each roll and supported thereby.

References Cited in the file of this patent UNITED STATES PATENTS959,120 Dean May 24, 1910 1,101,728 Craft June 30, 1914 1,307,341Brinton June 24, 1919 1,733,504 I MacDonald Oct. 29, 1929 1,744,616Cunningham Jan. 21, 1930 2,121,600 Knowles June 21, 1938

